Laser Photolysis Studies on the Intramolecular Dimer Radical Cations Formed in 1,3-Dipyrenylpropanes

Article abstract of DOI:10.1021/j100168a017

The structure and stabilization energy of dimer radical cations of intramolecular and intermolecular pyrenyl compounds were estimated by nanosecond laser photolysis in visible and near-IR regions.Electron-transfer quenching of three intramolecular dipyrenyl compounds, 1,3-di(1-pyrenyl)propane (1Py1Py), 1-(1-pyrenyl)-3-(2-pyrenyl)propane (1Py2Py), and 1,3-di(2-pyrenyl)propane (2Py2Py), produced the intramolecular dimer radical cation in an acetonitrile solution.The charge resonance (CR) band of dimer radical cations of 1Py1Py and 2Py2Py was located at 1600 nm, and this structure was ascribed to the full-overlap conformation of two pyrenyl groups.On the other hand, 1Py2Py formed a partial-overlap dimer cation radical whose CR band appeared at >2200 nm, which indicates a stability of ca. 2.4 kcal mol^-1 less than that of the full-overlap type.The intermolecular pyrene (Py) dimer radical cation had a CR band at 1450-nm peak and was ca. 0.9 kcal mol^-1 more stable than the full-overlap structure of 1Py1Py and 2Py2Py dimer radical cations.This conformation of intermolecular Py dimer radical cations was ascribed to a distorted conformation.